The UTRAN (Universal Terrestrial Radio Access Network) is currently standardized in the 3GPP (3rd Generation Partnership Projects).
FIG. 1 shows an example of the architecture of a wireless communication system in which UTRAN is applied.
As shown in FIG. 1, UTRAN 60 is connected to core network 50. In addition, UTRAN is composed of a plurality of RNS (Radio Network Subsystems) 70.
Each of RNS 70 is made up from RNC (Radio Network Controller) 80 and a plurality of NodeB 90 that are wireless base stations. NodeB 90 carries out wireless communication with UE (User Equipment) 10, which is a mobile terminal.
In addition, UTRAN LTE (Long Term Evolution) is being investigated in recent 3GPP standardization with the aim of maintaining the competitiveness of UTRAN with the development of other wireless communication technologies such as wireless LAN (Local Area Networks) (Non-Patent Document 1).
FIG. 2 shows an example of the architecture of a wireless communication system in which UTRAN LTE is applied.
As shown in FIG. 2, in UTRAN LTE, UTRAN is made up by a plurality of eNB 20 that are wireless base stations realized by unifying RNC and Node B.
In UTRAN LTE, UTRAN is defined as E-UTRAN (Evolution-UTRAN) 30, and the core network and control functional unit are defined as MME (Mobility Management Entity) 40.
In UTRAN LTE, the interface between eNB 20 and MME 40 is defined as S1, the interface between eNB 20 is defined as X2, and the interface between eNB 20 and UE 10 is defined as Uu.
As described above, the unification of RNC and NodeB in UTRAN LTE results in a decrease of the number of nodes of E-UTRAN 30 compared to UTRAN 60 of FIG. 1.
The reduction of the number of nodes in UTRAN LTE results in a corresponding decrease of the setting delay of connections between UE 10/eNB 20/MME 40 for realizing communication by UE 10 (Non-Patent Document 2). This reduction is realized because the setting of connections between RNC 80/NodeB 90 in UTRAN 60 of FIG. 1 is unnecessary in E-UTRAN 30 of FIG. 2.
However, UE 10 must receive notification information that is distributed by broadcast from eNB 20 in order to establish a call with eNB 20. The notification information is the minimum necessary setting information for establishing a call by UE 10 and includes, for example, a parameter indicating the transmission power of the transmission signal from UE 10 to eNB 20 and a parameter indicating regulation information relating to the regulation of access from UE 10 to eNB 20.
For example, UE 10 receives notification information upon activation of UE 10, cell reselection, completion of handover, recovery from coverage, and alteration of notification information (Non-Patent Document 3).
FIG. 3 shows an example of the notification information reception sequence in UTRAN LTE.
As shown in FIG. 3, when altering notification information, eNB 20 appends information communicating the alteration of notification information to a paging signal and transmits an RRC (Radio Resource Control) message of the paging signal to UE 10 in Step E11.
After receiving the RRC message of the paging signal to which information has been appended that reports the alteration of notification information from eNB 20, UE 10 receives the RRC message of the notification information that has been altered in Steps E12-E14.
The notification information is composed of MIB (Master Information Block), SIBtype1 (System Information Block Type1), and SI (System Information). The above-described parameters are appended to the SIBtype1 or SI.
When the notification information has been altered, UE 10 receives the MIB and SIBtype1, or alternatively, receives the SI only when the System Information Value Tag (hereinbelow referred to as the Value Tag) of the SIBtype1 differs from the Value Tag of the notification information before alteration. The Value Tag is identification information for identifying notification information, and for example, is the version number of the notification information.
Based on the notification information that was received as described above, UE 10 then carries out processes for establishing the call with eNB 20, i.e., for establishing an RRC Connection.
FIG. 4 shows an example of the RRC Connection establishment sequence in UTRAN LTE.
As shown in FIG. 4, UE 10 first transmits a RACH (Random Access Characteristic) Preamble message to eNB 20 in Step F11, and then receives a RACH Response message from eNB 20 in Step F12. By means of this RACH procedure, UE 10 acquires an ID for transmitting the RRC message.
UE 10 next transmits an RRC Connection Request message requesting the establishment of a call to eNB 20 in Step F13.
When the call is to be established, eNB 20 transmits an RRC Connection Setup message that establishes the call to UE 10 in Step F14.
Then, when the call has been established, UE 10 transmits an RRC Connection Setup Complete message reporting that the establishment of the call has been completed to eNB 20 in Step F15.